A plastic pipe is formed in straight tubular forms of various sizes. In order to join the plastic pipe without the necessity of having a special outside coupling, it is necessary to form a bell in the end of the pipe such that it will receive the plain end of an adjoining pipe. The bell is formed by expanding the pipe outwardly such that the inside diameter of the bell is equal to the outside diameter of the pipe. In order to seal about the end of the pipe, a resilient O-ring is usually secured in a groove formed in the interior wall of the bell.
Heretofore, devices for forming the end of the pipe have been of the type which positions a retractable mandrel into the pipe and expands the mandrel outwardly by a screw or other similar device, thus pushing the pipe into a exterior mold cavity which is clamped about the end of the pipe. This is a cumbersome process which requires extensive molding equipment having many moving parts which wear out.